Over the last few days, thousands of people have taken to the Internet to play Sherlock Holmes.
Armed with little more than grainy surveillance camera videos, cellphone photos and live tweets from police scanners, they have flooded the Web with clues, tips and speculation about what happened in Boston and who might have been behind it.
Monday's bombings, the first major terrorist attack on American soil in the age of smartphones, Twitter and Facebook, provided an opportunity for everyone to get involved. Within seconds of the first explosion, the Internet was alive with the collective ideas and reactions of the masses.
But this watershed moment for social media quickly spiraled out of control. Legions of Web sleuths cast suspicion on at least four innocent people, spread innumerable bad tips and heightened the sense of panic and paranoia.
"This is one of the most alarming social media events of our time," said Siva Vaidhyanathan, a media studies professor at the University of Virginia. "We're really good at uploading images and unleashing amateurs, but we're not good with the social norms that would protect the innocent."
Even as first responders were struggling to tend to the needs of the three killed and more than 170 injured in the Boston Marathon blasts, Web forums were cranking out rumors that there had been four bombs instead of two, that an area library had been targeted and that the death count was well over a dozen.
In short order, forums like Reddit and 4chan were alive with speculation — based on little or no evidence — that the culprits were Muslim fundamentalists or perhaps right-wing extremists.
In a mad rush to be the first to identify the perpetrators, anonymous posters online began openly naming people they believed had planted the bombs. Caught up in the mania, some traditional media ran with that information. Thursday's New York Post cover showed a photo of two men at the marathon under the headline "Bag Men" and implied that the two were prime suspects. In fact, neither was a suspect and one of the men, Salah Barhoun, was a high school student from outside Boston and had nothing to do with the explosions.
Once the FBI released images of the actual suspects, things really got out of hand. Online gumshoes scoured the Web for faces that might match and illustrated their work with drawings, circles and other home-brewed CSI techniques.
Some amateur sleuths focused their suspicions on Sunil Tripathi, a Brown University student who has been missing since last month. Using an animation tool, they used an image of Tripathi to highlight similarities between his face and the FBI photos of one of the Boston bombing suspects.
However, Tripathi has no apparent connection to the marathon bombing. That was underscored Friday, when authorities revealed the identities of their suspects, two ethnic-Chechen immigrant brothers — Tamerlan Tsarnaev, 26, and Dzhokhar Tsarnaev of Cambridge, Mass.
"We have known unequivocally all along that neither individual suspected as responsible for the Boston Marathon bombings was Sunil," Tripathi's family said in a statement on Friday.
Advocates of social media and crowd-sourcing have long touted its unrivaled power to gather huge amounts of information quickly in crisis situations. With tens of thousands of people on hand at the marathon, most armed with smartphones, the sheer volume of data available for analysis proved too tempting to ignore.
"People in the moment want to participate. They want to be a part of what's going on," said Nicco Mele, an expert on technology and social media at Harvard's John F. Kennedy School of Government.
So as the Boston Police Department engaged in a gunfight with the two brothers in Watertown, Mass., early Friday, tens of thousands of Web denizens tuned in to live streams of police scanners, furiously tapping notes and ideas into Reddit and Twitter.
"I feel like we've reached a certain threshold here — the Internet is finally outstripping cable news completely," a poster using the handle PantsGrenades wrote on Reddit. "In fact, I wonder if we're inadvertently doing their work for them."
Their speculation was not limited to the events in Boston. The unusual confluence of tragic and suspicious events in the past week led many online to suggest that the fertilizer plant explosion in West, Texas, might have been a terrorist attack as well and that the ricin-laced letters mailed to politicians could have come from those behind the marathon bombing.
According to Murray Jennex, a crisis management expert at San Diego State University, the huge influx of online voices enabled by social media can be extremely helpful because eye witnesses are holding cameras in almost every location.
But beyond the photos they upload, their speculation and theorizing don't necessarily lead to a more efficient resolution.
"There is just a lot of meaningless noise out there," he said, noting that law enforcement and disaster management institutions can be overwhelmed by useless tips in a crisis. "People see trends and patterns that aren't really trends and patterns."
Another problem with social media, he said, is that there is no way to tell who is a reliable source of information and who isn't. "People love to speculate and some people love to make the Web equivalent of crank calls."
On Friday morning, the Boston Police temporarily pulled the online feed of their scanners and tweeted several warnings to the public to not endanger their investigation and officer safety with reckless online commentary.
And a growing backlash against the finger pointing and public shaming that spewed forth from online forums caused some posters to be chastened. "Reminder," one Reddit user posted. "Do not post personal
information in the comments. This is raw incoming news, you could ruin an innocent person's life by spreading an incorrect name around."
But in many ways it was too late. The Internet is forever, as the saying goes, and the names of the innocent had already been circulated.
Experts say that the role of social media in crisis situations is only bound to grow as smartphones proliferate further and the public continues to clamor for instantaneous information.
"The instinct is to satisfy our voyeuristic urges," said the University of Virginia's Vaidhyanathan.